Not to worry, Penny, your record remains unblemished. As Eric pointed out, Charlie is correct that after one positive test, the probability that you have the disease is 50%.Positive means "the test shows you have the disease"

There are two ways the test could be positive:(A): The test was accurate and you have the disease(B): The test was wrong and you are disease free.

In each case the likelihood in the general population is .01*.99, so Prob(A) = Prob(B) and therefore 50:50 that you have the disease.But note that after zero tests, your probability of disease is 1%, and after one positive test it's up to 50%, so go ahead and worry a little (enough to get re-tested), just don't do a Ben Gazarra and make any life changing decisions.